[Tilecache] Re: MetaTiling - does projection affect?

[Eric Lemoine]

On Thu, May 6, 2010 at 2:07 PM,  <christopher.schmidt at nokia.com> wrote:
>
> On May 6, 2010, at 8:18 AM, ext Eric Lemoine wrote:
>
>> On Thu, May 6, 2010 at 12:27 PM, christopher.schmidt at nokia.com
>> <christopher.schmidt at nokia.com> wrote:
>>> [...] TileCache performs local locking to prevent re-requesting the same area multiple times.
>>
>> Quick question: does TileCache use this locking mechanism for meta
>> tiles only? If so why?
>
> Yes, and because locking didn't exist when the single tile mechanism was written. (Also, it creates significantly more disk access with a relatively limited gain on 'fast' tiles, which was the primary test case.)
>
> I wouldn't be against adding locking to the non-metaTiling case, either by default or as an option, though I'd rather have it as an option because of the increased disk usage.
>
> Also, note that locking in the single tile case is only helpful when there are multiple accessors of the same tile at once, while the tile is ungenerated; the metaTile case, this is the default behavior with any tiling client, so the need there is obviously greater. (Requesting 25 metaTiles instead of one, with the corresponding 25x execution time on the server, would really not work well; even when you realize that render time doesn't scale linearly with area, it's still not a great way to go.)


This makes great sense. Thanks,



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Eric Lemoine

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